Patent Document 1 discloses an example of an RFID medium (a contactless information medium) such as a contactless IC card which performs wireless communication using signals in an HF band (for example, 13.56 MHz). An antenna pattern of an antenna coil of such an RFID medium can be designed in any shape as long as the functional requirements for performing wireless communications with external devices are met.
Certain restrictions may be imposed on the antenna pattern in order to meet the requirements of a shape or a specific standard of an object to which the RFID medium is to be installed. For example, in the standard specified as ISO/IEC 14443-1, Class 1, an area where an antenna pattern can be arranged is set in order to provide an opening (a region having no wiring pattern) formed inside an antenna coil. Specifically, in the above standard, the area where the antenna pattern can be arranged is set to be an annular area obtained by removing, from a rectangular region having a length of 49 mm and a width of 81 mm, a substantially rectangular region having a length of 34 mm and a width of 64 mm (this rectangular region having corners rounded with R3 mm) and centered in the rectangular region.